alone is modified and not the
germinal substance for the next generation within this body. Such
responses to environing conditions do not affect nor involve the
structure of the germ, and are therefore unrepresented in that series
of reactions that result in the production of an individual of the
next generation. In this class are found most of the instances of
"functional modification" or acquired characteristics. In this
category belong most of the stock illustrations--from the blacksmith's
arm and the pianist's fingers, to the giraffe's neck and the fox's
cunning. Here also belong the results of training and education; we
can train and educate brain cells but not germ cells.

It is characteristic of most of these bodily reactions to external
conditions that they are adaptive; that is, when a body reacts to
such a condition it does so by undergoing a change which makes the
organism better fitted to the new condition--better able to exist. The
increased keenness of vision, the strengthened muscle, the thickened
fur--all such changes meet new or unusual demands in such a way that
the organism has better chances of survival than it would have had
unmodified.

But in the second place there are certain environmental circumstances
which do affect the structure of the germinal substance within the
body of an organism. An unusually high temperature acting at a certain
period in the life-history may bring about a change in the color of
insects which is heritable--i. e., racial; but such a change results
from the action of temperature upon the germ directly and not alone
upon the body, which then itself affects the germ. It is essential to
recognize that in all such cases it is not the structural change in
the body that affects the germ, but it is the external condition
itself that affects the germ directly. This is not the half of a hair;
it is an extremely important and significant difference. The effects
of this kind of action are not visible until the generation following
that acted upon. They become expressed in the bodies of the organisms
developed from the affected germs.

It is characteristic of such changes as these that they may not,
usually do not, have an adaptive relation to the condition bringing
about the change. There is no correspondence between the bodily and
the germinal modifications resulting from the action of the same
condition. Furthermore, there seems to be no adaptive relation between
the general c